Electron beam multiplication tube



Dec. 28, 1965 J. w. GRIFFITH ELECTRON BEAM MULTIPLICATION TUBE Filed July 8, 1960 H E. hN

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United States Patent 3,226,594 ELECTRON BEAM MULTIPLICATIGN TUBE Joseph W. Griffith, 12335 SW. Faircrest, Beaverton, Oreg. Filed July 8, 1960, Ser. No. 41,575 Claims. (Cl. 315-85) This invention pertains to analog multiplication devices, and relates particularly to an improved electron beam multiplication tube of the type disclosed by E. J. Angelo, Jr. in Technical Report No. 249 dated October 27, 1952 from Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, and entitled An Electron-Beam Tube for Analog Multiplication.

It is a principal object of the present invention to provide a multiplication tube of the class described, which tube is characterized by greater precision of operation with substantial reduction of structural complication and size.

Another important object of this invention is the provision, in a multiplication tube of the class described, of means for automatically indicating or correcting errors due to current non-uniformity at the target.

Still another important object of the present invention is the provision of a multiplication tube of the class described which aifords visual inspection of the size, shape and position of the electron beam spot impinging upon the target.

A further important object of this invention is the provision, in a multiplication tube of the class described, of means by which to achieve uniform diifusion of electrons at the target, and corresponding maximum uniformity of current in the electron beam at the target.

A still further important object of the present invention is the provision, in a cathode ray tube, of an improved deflecting system by which to achieve simultaneous deflec tion of electrons in the x and y planes.

A further important object of the present invention is to provide a multiplication tube of the class described which is of simplified construction for economical manufacture, which is capable of prolonged usage with a minimum of maintenance and repair, and which is of compact design 7 for maximum utility.

' tion, taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic View of a multiplication tube embodying the features of this invention;

FIG. 2 is a front view of the target component of the tube as viewed in the direction of the arrows 22 in FIG. 1;

FIG. 3 is an end view of the simultaneous deflection component of the tube as viewed in the direction of the arrows 3-3 in FIG. 3;

. FIG. 4 is an end view similar to FIG. 3 and showing a modified form of simultaneous deflection system;

FIG. 5 is an end view similar to FIG. 3 and showing a further modified form of simultaneous deflection system; and

FIG. 6 is a fragmentary sectional view of the forward end 'of a multiplication tube and showing a modified form of target associated therewith.

Referring principally to FIG. 1 of the drawing, the multiplication tube is in the general form of a cathode ray tube, and includes an evacuated glass envelope 1t) sealed to the tube base 12. Within the envelope there are included the usual components of an electron gun namely a cathode 14, a control grid 16, anodes 18 and 20, focusing electrode 22 and deflection system 24. These components are supported within the tube in well-known manner and connected electrically to the corresponding base prongs 26.

Adjacent the forward end of the tube there is provided a collector target made up of four electrically conductive quadrants 30, 32, 34 and 36 electrically insulated from each other. Electrical conductors 30', 32, 34' and 36' are connected to the associated quadrants, and these conductors project outwardly through the tube envelope for connection to a suitable meter or other indicator by which to identify the output current or voltage, in the manner now to be described.

The mode of operation of the multiplication tube is described in detail in the reference mentioned hereinbefore. A brief description is presented here, with reference particularly to FIG. 2.

The beam of electrons emitted from the cathode 14 impinge upon the target in the form of an enlarged spot 49 having substantially uniform electron current density. The spot is in the shape of a circle or other form which is symmetrical about x and y axes. Initially this spot is adjusted to a position concentric with the axial center of the target.

Voltages applied to the x and y quadrants of the deflection system 24 causes the spot 40 to shift parallel to the x and y axes of the target quadrants, thus displacing the center 40 of the spot from the axial center of the target. In FIG. 2, the spot is shown to be displaced in such manner that its center is positioned within the quadrant 30.

By designating the quadrants positive and negative, as shown, the algebraic sum of the currents collected by the quadrants is proportional to the product of the displacement of the center of the spot from the center of the target along the x and y axes. This is established in the following manner: The dotted lines 42 and 44 indicated in FIG. 2 are drawn parallel to the x and y axes at the positions 2x and 2y. The pairs of areas a and a, b and b, c and c bounding these dotted lines are disposed in quadrants having opposite signs, and hence the currents falling in these pairs of areas cancel each other. The current remaining'is contributed only by the rectangular area 2x, 2y, and this current is 4rl(xy) wherein d is the constant current density. Thus, the output signal is directly proportional to the product of the two input voltages applied to the x and y deflection quadrants.

In accordance with the present invention, the target quadrants are carried upon an electrically non-conductive plate supported within the envelope 10 in well known manner. The material for the target may be electrically conductive metal, such as gold, silver, platinum and others, or it may be electrically conductive salts such as tin orthosilicate and others.

In the formation of the target, the electrically conductive material is applied to the plate by such means as physical attachment of metal foil, or by deposition by the evaporation of metal onto the plate, or by the painting of electrically conductive material upon the support. The coating then is cut along precise perpendicular lines to provide the insulating barriers 52 which separate the quadrants electrically from each other.

By coating the target quadrants with semi-conductive material 54 characterized by a low ratio of secondary to primary electrons, the deleterious effect of secondary emission is reduced to a minimum. Semi-conductive materials suitable for this purpose are zinc orthosilicate, vinadium pent oxide, chromium and feric oxides, mixtures of the foregoing and many others well known in the art. By thus minimizing secondary emission, physical barriers between the quadrants are unnecessary and therefore limitations imposed by the latter are avoided.

Although the accuracy of multiplication is independent of the width of the insulating barriers 52 between quadrants, the useful current in the electron beam is reduced by the amount of current intercepted by the barriers. This reduction of useful current is minimized substantially in the present invention, since the width of the insulating barriers between quadrants need only be that resulting from cutting of the target material.

An alternative form of target construction is illustrated in FIG. 6. The forward end ill of the glass envelope is flattened to provide support for the electrically conductive target quadrants. T he associated electrical conductors are brought out through the wall of the envelope. The target quadrants are provided by a thin film of electrically conductive material, such as the metals or salts mentioned hereinbefore, and these thin films are sufficiently translucent as to render visible through the front end of the envelope the glowing spot resulting from impingement of the electron beam upon a phosphorescent coating 56 applied over the surface of the target quadrants. This arrangement permits visual inspection of the size, shape and position of the electron beam on the target.

In the embodiment illustrated in FIG. 1, means is provided for automatically indicating or correcting product errors resulting from non-uniform current distribution throughout the electron beam. Such means is provided by a small Faraday cup sa positioned in back of the target plate 50 in alignment with a tiny aperture 62. which extends through the plate at the center of the target. Thus, a tiny portion of the electron beam is sampled through the aperture and the current collected at the cup. This cup is connected through the resistance 64 to a source of voltage which is positive with respect to the cathode 14. The current sample is applied to the input of a feedback amplifier 66, the output of which may simply be connected to a microammeter for visual reading of current deviations, or it may be connected to an appropriate component of the electron gun, such as the control grid 16, in such manner that the deviation functions automatically to correct the product error. Alternatively, the current deviation may be applied to the electron gun in such manner as to cut oif the electron beam so that no product is provided at the target.

It will be apparent that the Faraday cup may be provided for the target construction shown in FIG. 6 by simply forming the central portion of the front end it? of the envelope with a forwardly projecting cavity for housing the cup. Since the cup is much smaller than the electron beam spot 40, it does not interfere appreciably with the visual inspection of the spot.

For maximum precision of operation of the multiplication tube, it is preferred that the components of the electron gun be operated, by application of proper voltages, in such manner that the electrons emitted from the cathode 14 are caused to converge, for example in the region of the first anode 18, whereby the mutual repulsion between electrons subsequently effects their uniform diffusion throughout the beam and results in substantially uniform current distribution at the target. Whatever small degree of non-uniformity still might exist, may be accounted for or corrected by sampling a small portion of the electrons in the electron beam, by means of the Faraday cup, as previously explained.

Although conventional electrostatic deflection systems utilizing longitudinally spaced horizontal and vertical deflection plates may be employed in the multiplication tube, a simultaneous deflection system of this invention is preferred not only for the resulting reduction of tube size to minimum dimensions, but also for achieving greater accuracy of multiplication.

The simultaneous deflection system of this invention reduces to a minimum the non-symmetrical distortions inherent in the aforementioned conventional systems. This is important in the present invention since it is essential that the configuration of the electron beam at the target be substantially symmetrical about the x and y axes of the target quadrants.

ln the embodiment illustr ted in FIGS. 1 and 3, the simultaneous deflection system is provided by Wrapping uniform resistance wire as about an electrically nonconducting hollow support 71, and connecting the terminal ends of the wire together. Although the hollow support may be of any desired configuration, such as a circular or square cylinder, truncated cone, and others, the form illustrated in FIGS. 1 and 3 is a truncated pyramid which flares in the direction of the target. Electrical conductors 72, 74 and 76, 78 are tapped to the resistance winding to form opposed pairs 8i and 82 of quadrants. The electrical conductors associated with the quadrant pairs are connected to the sources of x and y deflection voltages which, as explained more fully hereinafter, are chosen to be proportional to the quantities to be multiplied.

By applying a portion of the x deflection voltatge to the y quadrants and a portion of the y deflection voltage to the x quadrants, the deflection axes may be positioned to coincide precisely with the axes of the target, thus eliminating the requirement for precise alignment of the physical components in the tube.

The form of simultaneous deflection system i lustrated in FIG. 4 comprises a truncated cone fll of electrically non-conductive material having on its outer surface a coating 92 of uniform resistance material. Elec rically conductive wires or rods 94 are bonded to this resistive coating at intervals to provide opposing pairs $6 and 93 of quadrants affording x and y deflection, as described hereinbefore.

The simultaneous deflection system illustrated in FIG. 5 comprises opposed pairs liiil and 102 of electrically conductive plates having curved cross sectional configurations. in the embodiment illustrated these configurations are hyperbolic, although it will be understood that they may be parabolic, arcuate, or any other desired shape developed from a conical section.

The deflection systems illustrated in S. 3 and 4 and utilizing uniform resistance deflection quadrants, are preferred over the curved conductive plate system shown in FIG. 5. The uniform resistance quadrants provides an infinite number of equipc-tential plane surfaces, and this result is obtainable in the system of FIG. 5 only to the degree of precision with which the curved surfaces are formed.

The tube of this int tion has many uses other than general high speed analog computation. Typical of such other uses, in which m "-on is involved, are modulation, detection, power measurement, cross-correlation, auto-correlation and others.

it will be apparent to th se skilled in the art that vario 3 changes in the details of construction described hereiribefore may be made Without departing from the spirit of this invention and the scope of the appended claims.

Having now described my invention and the manner in which it may be used, what I claim as new and desire to secure by Letters Patent is:

l. in a multiplication tube having an electron gun adapted to provide a beam of electrons that is substantially symmetrical about x and y axes and an electron beam deflection system responsive to a pair of signals to be multiplied: an electron collecting target comprising spaced quadrants of electrically conductive material, the spacing between quadrants insulating the latter from each other, the target and beam being so proportioned that the beam is substantially larger in dimension than the spacing between target quadrants, and a coating of material haracterized by a low ratio of secondary to primary electrons bonded to the target quadrants for minimizing emission of secondary electrons.

Z. In a multiplication tube having an electron gun adapted to provide a beam of electrons that is substantially symmetrical about it and y axes and an electron beam deflection system responsive to a pair of signals to be multiplied: an electron collecting target comprising electrically conductive material severed along perpendicular lines to provide spaced quadrants, the spacing between quadrants insulating the latter from each other, the target and beam being so proportioned that the beam is substantially larger in dimension than the spacing between target quadrants, and .a coating of material characterized by a low ratio of secondary to primary electrons bonded to the target quadrants for minimizing such emission of secondary electrons.

3. In a multiplication tube having an electron gun adapted to provide a beam of electrons that is substantially symmetrical about x and y axes and an electron beam deflection system responsive to a pair of signals to be multiplied: an electron collecting target comprising spaced quadrants of electrically conductive substantially translucent material, the spacing between quadrants insulating the latter from each other, the target and beam being so proportioned that the beam is substantially larger in dimension than the spacing between target quadrants, and a coating of phosphorescent material characterized by a low ratio of secondary to primary electrons on the target quadrants to render the electron beam visible at the target and to minimize emission of secondary electrons.

4. In a multiplication tube having an electron gun adapted to provide a beam of electrons that is substantially symmetrical about x and y axes, an electron beam deflection system responsive to -a pair of signals to be multiplied and an electron collecting target mounted upon an electrically non-conducting support and comprising electrically conductive quadrants insulated from each other and arranged to receive the electron beam: sample collector means associated with the target for receiving a portion of the electrons in the beam and comprising an electrically conductive collector member disposed behind the support in alignment with a central aperture in the support, and error signal means associated with the. sam ple collector means and responsive to variations in current density of the sampled beam to provide an error signal.

5. The multiplication tube of claim 4 including means connecting the error signal means to the electron gun for automatically correcting the variations in current density of the sampled beam.

References Cited by the Examiner UNITED STATES PATENTS 2,179,097 11/1939 Law 313-78 2,344,679 3/1944 Crosby 315-21 X 2,474,810 7/ 1949 Arditi et al 315-21 X 2,527,512 10/1950 Arditi 315-21 2,534,372 12/1950 Ring 315-8.5 2,578,458 12/195 1 Thompson 315-21 2,583,000 1/ 1952 Lytle 313-92 2,710,361 6/1955 Skellett 315-21 2,810,860 10/1957 Mork 315-27 2,834,902 5/ 1958 Gundert 313-78 2,897,393 7/1959 Iorio 313-78 X 2,904,712 9/ 1959 Schlesinger 313-78 JOHN W. HUCKERT, Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, DAVID J.

GALVIN, Examiners. 

1. IN A MULTIPLICATION TUBE HAVING AN ELECTRON GUN ADAPTED TO PROVIDE A BEAM OF ELECTRONS THAT IS SUBSTANTIALL SYMMETRICAL ABOUT X AND Y AXES AND AN ELECTRON BEAM DEFLECTION SYSTEM RESPONSIVE TO A PAIR OF SIGNALS TO BE MULTIPLIED: AN ELECTRON COLLECTING TARGET COMPRISING SPACED QUADRANTS OF ELECTRICALLY CONDUCTIVE MATERIAL, THE SPACING BETWEEN QUADRANTS INSULATING THE LATTER FROM EACH OTHER, THE TAQGET AND BEAM BEING SO PROPORTIONED THAT THE BEAM IS SUBSTANTIALLY LARGER IN DIMENSION THAN THE SPACING BETWEEN TARGET QUADRANTS, AND A COATING OF MATERIAL CHARACTERIZED BY A LOW RATIO OF SECONDARY TO PRIMARY ELECTRONS BONDED TO THE TARGET QUADRANTS FOR MINIMIZING EMISION OF SECONDARY ELECTRONS. 